As shown in FIG. 5, a prior art fan is shown. The fan 1 is directly positioned and fixed to a casing 2 of a computer. In a more original way, the fan 1 is installed at a position of a power source. The fan 1 is primarily used to dissipate heat of a computer. Even the central processing unit has a dedicated fan. The function of the fan serves to transfer the heat generated in the computer case to outer environment for reducing temperature in the computer case so that the mother board and interface board in the computer casing has a preferred operational environment. Even in an air conditioned room, the computer remains to dissipate heat, otherwise the heat will accumulated in the computer casing so that the temperature within the casing will increase. This is disadvantageous for the operation of a computer. The chips in an electronic device is more necessary to dissipate heat. If the temperature is too high, the operations and signal transformation will be unsteady, some problems will occur. This is possible to affect the operation speed of the computer. Even the computer possibly shuts down. This has a bad effect to the use of information. Therefore, it is a basic demand for a computer to dissipate heat normally and uninterrupted so that the components can be used efficiently. This is especially important for industrial computers.